Electrostatic reproduction involves an electrostatically-formed latent image on a photoconductive member, or photoreceptor. The latent image is developed by bringing charged developer materials into contact with the photoconductive member. The developer materials can include two-component developer materials including carrier particles and charged toner particles for such as “hybrid scavengeless development” having an image-on-image development. The developer materials can also include single-component developer materials including only toner particles. The toner particles adhere directly to a donor roll by electrostatic charges from a magnet or developer roll and are transferred to the photoconductive member from a toner cloud generated in the gap between the photoreceptor and the donor roll during the development process.
A conventional donor roll uses wire electrodes to generate toner clouds. Generally, AC biased wires have been used to provide electrostatic forces to release the toner particles from the donor roll. However, there are several problems with wires. First, toner particles tend to adhere to the wire after prolonged usage even with a non-stick coating on the wires. The adhered toner particles may cause image defects. Secondly, it is not easy to keep the wire clean once the wire is contaminated with toner components. Thirdly, it is difficult to build long wires on the roll for large format printing.
Piezoelectric materials, especially piezoelectric ceramics such as PZT (lead zirconate titanate), can effectively transfer electrical energy to mechanical energy or vice versa, and can be used in electrophotographic printing machines. However, it is difficult to make or mount a large area ceramic piece on a curved surface or embed it in a structure which needs to be flexible. Also it is difficult to put many piezoelectric elements with different shapes together to make a large area array with each element addressable.
Thus, there is a need to overcome these and other problems of the prior art and to provide a roll member using 2-dimensional addressable piezoelectric actuators in a large area and with different shapes.